B. Lal, R. Gidwani
1993
Citations
0
Influential Citations
1
Citations
Journal
Tetrahedron
Abstract
Abstract Substituted 6-(4,5-dimethoxy-2-vinylphenyl)-2,4-(1H, 3H) pyrimidinediones ( 2 ) undergo ring closure in the presence of a mixture of formic acid and orthophosphoric acid, to give 5H-indeno[1,2- d ]pyrimidines ( 3 ) and/or pyrimido[6,1- a ]isoindoles ( 4 ). Cyclization to 3 and/or 4 depends on the nature of substitution in the pyrimidine ring in 2 . Electron withdrawing groups at position 4 in 2 favour the formation of the skeleton 3 , however, electron donating groups gave more of 4 . Compound 2a on acid treatment, gave in addition to 3a , a dimeric product 5 . Phosphorus oxychloride treatment of compound 3a generated the 2,4-dichloro compound 7 . Two chloro groups behaved differently in their chemical reactivity. When 7 reacted with amines in benzene, generally 2-positional regioisomers predominated, however, in amyl alcohol 2,4-disubstituted amino compounds were formed.